DoFn.TimerId (core 2.44.0 API)

```
@Documented
@Retention(RUNTIME)
@Target({FIELD,PARAMETER})
@Experimental(TIMERS)
public static @interface DoFn.TimerId
```
Annotation for declaring and dereferencing timers.
To declare a timer, create a field of type TimerSpec annotated with a DoFn.TimerId. To use the cell during processing, add a parameter of the type Timer to your @ProcessElement or @OnTimer method, and annotate it with DoFn.TimerId. See the following code for an example:
```
new DoFn<KV<Key, Foo>, Baz>() {
   @TimerId("my-timer-id")
    private final TimerSpec myTimer = TimerSpecs.timerForDomain(TimeDomain.EVENT_TIME);

   @ProcessElement
    public void processElement(
       @Element InputT element,
       @TimerId("my-timer-id") Timer myTimer) {
      myTimer.offset(Duration.standardSeconds(...)).setRelative();
    }

   @OnTimer("my-timer-id")
    public void onMyTimer() {
      ...
    }
 }
```
Timers are subject to the following validity conditions:
- Each timer must have a distinct id.
- Any timer referenced in a parameter must be declared.
- Timer declarations must be final.
- All declared timers must have a corresponding callback annotated with @OnTimer.

- Optional Element Summary
  
  Optional Elements
  Modifier and Type Optional Element Description
  
  java.lang.String value
  The timer ID.

- Element Detail
  - value
```
java.lang.String value
```
    The timer ID.
    
    Default:
    
    ""